Wiring board and fabricating method thereof, semiconductor device and fabricating method thereof, circuit board and electronic instrument

ABSTRACT

A conductive material is provided to an open end of a penetrating hole penetrating through at least a semiconductor element, on the side of a first surface of the semiconductor element. The conductive material is melted to flow into the penetrating hole. The conductive material is made to flow into the penetrating hole in a state that an atmospheric pressure on the side of a second surface of the semiconductor element opposite to the first surface is lower than an atmospheric pressure on the side of the first surface.

Japanese Patent Application No. 63650/2001 filed on Mar. 7, 2001, ishereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

This invention relates to a wiring board and a fabricating methodthereof, a semiconductor device and a fabricating method thereof, acircuit board and an electronic instrument.

A form that electrically connects both surfaces of a semiconductor chipby boring penetrating holes in the semiconductor chip, forms aninsulating film and then forms either wet or dry an electricallyconductive film, or filling penetrating holes with molten solder isknown. Since this method eliminates the necessity for disposing wires, acompact semiconductor device can be acquired even when a plurality ofsemiconductor chips is stacked one upon another.

However, the process step of filling penetrating holes with a conductivematerial is often time consuming and troublesome. A method that forms afilm by means such as photolithography and renders the resulting filmelectrically conductive needs a large number of process steps, a longtime and a high cost of production. A method of filling penetratingholes of a wiring board with a conductive material is also known, butthe method needs a long time and troublesome procedures.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda method of fabricating a semiconductor device comprising the steps of:

providing a conductive material to an open end of a penetrating holepenetrating through at least a semiconductor element, on the side of afirst surface of the semiconductor element; and

melting the conductive material to make the conductive material flowinto the penetrating hole,

wherein the conductive material is made to flow into the penetratinghole in a state that an atmospheric pressure on the side of a secondsurface of the semiconductor element opposite to the first surface islower than an atmospheric pressure on the side of the first surface.

According to a second aspect of the present invention, there is provideda method of fabricating a stacked type semiconductor device comprisingthe steps of:

forming a plurality of semiconductor devices each of which is formed by:providing a conductive material to an open end of a penetrating holepenetrating through at least a semiconductor element, on the side of afirst surface of the semiconductor element; melting the conductivematerial to make the conductive material flow into the penetrating hole;and causing the conductive material to flow into the penetrating hole ina state that an atmospheric pressure on the side of a second surface ofthe semiconductor element opposite to the first surface is lower than anatmospheric pressure on the side of the first surface;

stacking the plurality of the semiconductor devices; and

electrically connecting the semiconductor elements of the stackedsemiconductor devices through the conductive material.

According to a third aspect of the present invention, there is provideda semiconductor device or a stacked type semiconductor device fabricatedby any of the above methods.

According to a fourth aspect of the present invention, there is provideda semiconductor device comprising:

a semiconductor element having a pad and a penetrating hole penetratingthrough the pad and the semiconductor element; and

a conductive material that is provided in an area including an innersurface of the penetrating hole and is electrically connected to thepad, wherein part of the conductive material forms a bump protrudingfrom a surface of the semiconductor element opposite to a surface havingthe pad.

According to a fifth aspect of the present invention, there is provideda stacked type semiconductor device comprising a plurality of stackedsemiconductor devices each of which includes:

a semiconductor element having a pad and a penetrating hole penetratingthrough the pad and the semiconductor element; and

a conductive material that is provided in an area including an innersurface of the penetrating hole and is electrically connected to thepad,

wherein part of the conductive material forms a bump protruding from asurface of the semiconductor element opposite to a surface of thesemiconductor element having the pad; and

wherein the semiconductor elements of the stacked semiconductor devicesare electrically connected through the conductive material.

A circuit board according to a sixth aspect of the present inventioncomprises the semiconductor device or the stacked type semiconductordevice described above.

An electronic instrument according to a seventh aspect of the presentinvention comprises the semiconductor device or the stacked typesemiconductor device described above.

According to an eighth aspect of the present invention, there isprovided a method of fabricating a wiring board comprising the steps of:

providing a conductive material to an open end of a penetrating holepenetrating through at least a board, on the side of a first surface ofthe board; and

melting the conductive material to make the conductive material flowinto the penetrating hole,

wherein the conductive material is made to flow into the penetratinghole in a state that an atmospheric pressure on the side of a secondsurface of the board opposite to the first surface is lower than anatmospheric pressure on the side of the first surface.

A wiring board according to a ninth aspect of the present invention isfabricated by the above described method.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIGS. 1A to 1C show a fabrication method of a semiconductor deviceaccording to the first embodiment of the present invention;

FIGS. 2A to 2C show a fabrication method of a semiconductor deviceaccording to the first embodiment of the present invention;

FIG. 3 shows a semiconductor device according to the first embodiment ofthe present invention;

FIG. 4 shows a semiconductor device according to the first embodiment ofthe present invention;

FIG. 5 shows a fabrication method of a semiconductor device according toa modification of the first embodiment of the present invention;

FIG. 6 shows a fabrication method of a semiconductor device according toanother modification of the first embodiment of the present invention;

FIG. 7 shows a fabrication method of a semiconductor device according tostill another modification of the first embodiment of the presentinvention;

FIGS. 8A to 8C show a fabrication method of a semiconductor deviceaccording to the second embodiment of the present invention;

FIGS. 9A to 9C show a fabrication method of a semiconductor deviceaccording to the third embodiment of the present invention;

FIG. 10 shows a circuit board to which a semiconductor device accordingto one embodiment of the present invention is mounted;

FIG. 11 shows an electronic instrument having a semiconductor deviceaccording to one embodiment of the present invention; and

FIG. 12 shows an electronic instrument having a semiconductor deviceaccording to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention may solve the problems describedabove, and provide a wiring board and its fabrication method, asemiconductor device and its fabrication method, a circuit board and anelectronic instrument, all of which are capable of easily providing anelectrically conductive material in a penetrating hole.

(1) According to one embodiment of the present invention, there isprovided a method of fabricating a semiconductor device comprising thesteps of:

providing a conductive material to an open end of a penetrating holepenetrating through at least a semiconductor element, on the side of afirst surface of the semiconductor element; and

melting the conductive material to make the conductive material flowinto the penetrating hole,

wherein the conductive material is made to flow into the penetratinghole in a state that an atmospheric pressure on the side of a secondsurface of the semiconductor element opposite to the first surface islower than an atmospheric pressure on the side of the first surface.

According to this embodiment, the molten conductive material flows intothe penetrating hole toward the side of the second surface having alower atmospheric pressure than the side of the first surface. Theconductive material can be made to flow in a short time into thepenetrating hole by controlling the difference of atmospheric pressure.

(2) In this method of fabricating a semiconductor device, thesemiconductor element may have a pad formed on the first surface; andthe penetrating hole may penetrate through the pad.

(3) In this method of fabricating a semiconductor device, a conductivefilm extending from the pad into an inner surface of the penetratinghole may be formed before the conductive material is provided.

The pad and the conductive material can be thus reliably connected.

(4) In this method of fabricating a semiconductor device, the conductivematerial may be a solid, and the solid conductive material may be placedover the open end of the penetrating hole on the side of the firstsurface.

Since it is only necessary to place the solid conductive material overthe penetrating hole, the stress resulting from pressurization does notact on the semiconductor element, and damage can be prevented.

(5) In this method of fabricating a semiconductor device, the conductivematerial may be paste-like, and the paste-like conductive material maybe applied to the open end of the penetrating hole on the side of thefirst surface.

(6) In this method of fabricating a semiconductor device, the paste-likeconductive material may be applied to the first surface of thesemiconductor element.

This configuration makes it possible to provide the conductive materialto the open end of the penetrating hole without consideration of theposition of the penetrating hole.

(7) In this method of fabricating a semiconductor device, a laser beammay be projected onto the conductive material to melt the conductivematerial.

Since partial heating can be conducted, it becomes possible to preventthe semiconductor element from being heated to a high temperature. It iseffective when there is possibility of damage of the semiconductorelement if it is heated as a whole.

(8) In this method of fabricating a semiconductor device, thesemiconductor element may be heated to melt the conductive material.

This makes it possible to easily melt the conductive material.

(9) In this method of fabricating a semiconductor device, the conductivematerial may be made to flow in a state that an atmospheric pressure onthe side of the first surface of the semiconductor element is higherthan normal atmospheric pressure.

(10) In this method of fabricating a semiconductor device, theconductive material may be made to flow in a state that an atmosphericpressure on the side of the second surface of the semiconductor elementis lower than normal atmospheric pressure.

(11) In this method of fabricating a semiconductor device, theconductive material may be made to flow through the penetrating hole andprotrude from the second surface into a bump.

When both surfaces of the semiconductor element are electricallyconnected by the conductive material, the bump can be formed in thesemiconductor element. Therefore, it is not necessary to provide a stepof forming a bump separately.

(12) In this method of fabricating a semiconductor device, thepenetrating hole may be formed as a hole in the semiconductor element,an inner wall of the hole being covered by an insulating material; andthe diameter of the bump may be smaller than the diameter of the hole.

In this configuration, the bump as a part of the conductive material hasa smaller diameter than the diameter of the hole. Therefore, it becomespossible to prevent the bump from swelling out of the area of theinsulating material to become electrically conductive with thesemiconductor element.

(13) In this method of fabricating a semiconductor device, thesemiconductor element may be a semiconductor wafer.

(14) According to one embodiment of the present invention, there isprovided a method of fabricating a stacked type semiconductor devicecomprising the steps of:

forming a plurality of semiconductor devices each of which is formed by:providing a conductive material to an open end of a penetrating holepenetrating through at least a semiconductor element, on the side of afirst surface of the semiconductor element; melting the conductivematerial to make the conductive material flow into the penetrating hole;and causing the conductive material to flow into the penetrating hole ina state that an atmospheric pressure on the side of a second surface ofthe semiconductor element opposite to the first surface is lower than anatmospheric pressure on the side of the first surface;

stacking the plurality of the semiconductor devices; and

electrically connecting the semiconductor elements of the stackedsemiconductor devices through the conductive material.

According to this embodiment of the invention, a semiconductor devicehaving a three-dimensional package can be fabricated at a low cost andthrough a simple process.

(15) According to one embodiment of the present invention, there isprovided a semiconductor device or a stacked type semiconductor devicefabricated by any of the above described methods.

(16) According to one embodiment of the present invention, there isprovided a semiconductor device comprising:

a semiconductor element having a pad and a penetrating hole penetratingthrough the pad and the semiconductor element; and

a conductive material that is provided in an area including an innersurface of the penetrating hole and is electrically connected to thepad,

wherein part of the conductive material forms a bump protruding from asurface of the semiconductor element opposite to a surface having thepad.

According to this embodiment, part of the conductive material providedin the penetrating hole protrudes from the surface of the semiconductorelement. Therefore, when the protruding portion is used as an externalterminal, for example, the number of components of the semiconductordevice can be reduced, and its fabrication process can be simplified,too. Therefore, a semiconductor device can be provided with a reducedcost.

(17) In this semiconductor device, the penetrating hole may be formed asa hole in the semiconductor element, an inner wall of the hole beingcovered by an insulating material; and the diameter of the bump may besmaller than the diameter of the hole.

In this configuration, the bump as a part of the conductive material hasa diameter smaller than that of the hole. Therefore, it is possible toprevent the bump from swelling out of the area of the insulatingmaterial to become electrically conductive with the semiconductorelement.

(18) In this semiconductor device, another part of the conductivematerial may protrude from the surface having the pad.

This configuration can decrease the number of components of thesemiconductor device if the protruding portion is used as an externalterminal.

(19) According to one embodiment of the present invention, there isprovided a stacked type semiconductor device comprising a plurality ofstacked semiconductor devices each of which includes:

a semiconductor element having a pad and a penetrating hole penetratingthrough the pad and the semiconductor element; and

a conductive material that is provided in an area including an innersurface of the penetrating hole and is electrically connected to thepad,

wherein part of the conductive material forms a bump protruding from asurface of the semiconductor element opposite to a surface of thesemiconductor element having the pad; and

wherein the semiconductor elements of the stacked semiconductor devicesare electrically connected through the conductive material.

According to this embodiment of the present invention, part of theconductive material provided in the penetrating hole protrudes from thesurface of the semiconductor element and this protruding portionelectrically connects the upper and lower semiconductor elements withone another. Therefore, the number of components of the semiconductordevice can be reduced, the fabrication process can be simplified andeventually, a semiconductor device can be provided with a reduced cost.

(20) A circuit board according to one embodiment of the presentinvention comprises the semiconductor device or the stacked typesemiconductor device described above.

(21) An electronic instrument according to one embodiment of the presentinvention comprises the semiconductor device or the stacked typesemiconductor device described above.

(22) According to one embodiment of the present invention, there isprovided a method of fabricating a wiring board comprising the steps of:

providing a conductive material to an open end of a penetrating holepenetrating through at least a board, on the side of a first surface ofthe board; and

melting the conductive material to make the conductive material flowinto the penetrating hole,

wherein the conductive material is made to flow into the penetratinghole in a state that an atmospheric pressure on the side of a secondsurface of the board opposite to the first surface is lower than anatmospheric pressure on the side of the first surface.

According to this embodiment of the present invention, the moltenconductive material can be made to flow into the penetrating hole towardthe side of the second surface having a lower pressure than the side ofthe first surface. Since this operation is conducted by controlling thepressure difference, the conductive material can be provided in thepenetrating hole in a short time.

(23) In this method of fabricating a wiring board, the board may have aland for an interconnecting pattern formed on the first surface; and thepenetrating hole may penetrate through the land for the interconnectingpattern.

(24) In this method of fabricating a wiring board, a conductive filmextending from the land to an inner surface of the penetrating hole maybe formed before the conductive material is provided.

This enables to electrically connect the land to the conductive materialreliably.

(25) In this method of fabricating a wiring board, the conductivematerial may be a solid, and the solid conductive material may be placedover the open end of the penetrating hole on the side of the firstsurface.

Since it is necessary only to put the solid conductive material over theopen end of the penetrating hole, the stress resulting frompressurization does not act on the substrate, and the substrate is notdamaged.

(26) In this method of fabricating a wiring board, the conductivematerial may be paste-like, and the paste-like conductive material maybe applied to the open end of the penetrating hole on the side of thefirst surface.

(27) In this method of fabricating a wiring board, the paste-likeconductive material may be applied to the first surface of the board.

This makes it possible to easily provide the conductive material overthe open end of the penetrating hole without consideration of theposition of the penetrating hole.

(28) In this method of fabricating a wiring board, a laser beam may beprojected onto the conductive material to melt the conductive material.

Since partial heating can be conducted, it becomes possible to preventthe substrate from being heated to a high temperature. Therefore, thesubstrate is not damaged.

(29) In this method of fabricating a wiring board, the board may beheated to melt the conductive material.

This makes it possible to easily melt the conductive material.

(30) In this method of fabricating a wiring board, the conductivematerial may be made to flow in a state that an atmospheric pressure onthe side of the first surface of the board is higher than normalatmospheric pressure.

(31) In this method of fabricating a wiring board, the conductivematerial may be made to flow in a state that an atmospheric pressure onthe side of the second surface of the board is lower than normalatmospheric pressure.

(32) In this method of fabricating a wiring board, the board may have aland for a second interconnecting pattern formed on the second surface;the penetrating hole may penetrate through the land for the secondinterconnecting pattern; and the conductive material may be electricallyconnected to the second interconnecting pattern in the step of makingthe conductive material to flow.

(33) In this method of fabricating a wiring board, the board may be aglass epoxy board.

(34) In this method of fabricating a wiring board, the board may be apolyimide board.

(35) According to one embodiment of the present invention, there isprovided a wiring board fabricated by the above described method.

Embodiments of the present invention will now be described in detailwith reference to the accompanying drawings. However, the presentinvention is not limited to the embodiments below.

First Embodiment

FIGS. 1A to 2C show a fabrication method of a semiconductor deviceaccording to the first embodiment of the invention. FIGS. 3 and 4 showthe semiconductor device according to this embodiment. FIGS. 5 to 7 showa semiconductor device and a production method according tomodifications of this embodiment. First, penetrating holes 24 are formedin such a fashion as to penetrate through at least a semiconductor chip10 as shown in FIGS. 1A to 2A.

As shown in FIG. 1A, the semiconductor chip 10 (semiconductor device) isprepared. The semiconductor chip 10 is a rectangle in most case, but itsshape is not limited and may be a sphere, for example. The semiconductorchip 10 may be cut to a thickness smaller than that of its originalsemiconductor chip 12 (or a semiconductor wafer). More specifically, thesurface of the semiconductor chip 10 that is opposite to the surface onwhich an integrated circuit (not shown) is to be formed (active surface)is cut. Cutting of the semiconductor chip 10 may be conducted eitherbefore or after dicing of the semiconductor wafer. Alternatively, amethod may be employed that forms, from a surface, grooves to a depthgreater than the thickness of the semiconductor chip 10 on thesemiconductor wafer, and cuts the back of the semiconductor wafer tosplit the wafer into a plurality of thin semiconductor chips 10.

The semiconductor chip 10 has a plurality of pads 14. Each pad 14 is anelectrode of an integrated circuit formed in the semiconductor chip 10.The pad 14 is formed in most cases on the surface of the semiconductorchip 10 having the integrated circuit. The pad 14 is preferably formedon the surface of the semiconductor chip 10 and outside the area of theintegrated circuit. Such an arrangement makes it possible to formpenetrating holes 24 (see FIG. 2A) that penetrate through thesemiconductor chip 10 and through the pads 14 while avoiding the area ofthe integrated circuit. Alternatively, the pad 14 maybe formed insidethe area of the integrated circuit. The pad 14 is made in most cases ofaluminum or copper. Note that a passivation film (not shown) may furtherbe formed on the surface of the semiconductor chip 10 on which the pads14 are formed.

A metal layer 16 may be provided on the electrode 14, whenevernecessary. The metal layer 16 can prevent oxidation of the pad 14. Themetal layer 16 may use a material having high wettability to solder.When the solder is applied to the pad 14, the molten solder can beprovided in the penetrating holes 24 under a satisfactory condition. Thematerial of the metal layer 16 is not limited, and may be a metalcontaining at least nickel or gold, for example.

A hole 18 is formed in each semiconductor chip 10 as shown in FIG. 1B.The hole 18 is used to provide an insulating material 22, and is formedin such a fashion as to penetrate through the semiconductor chip 10.Laser (YAG laser or excimer laser) may be used to form the hole 18. Alaser beam may be irradiated from the surface of the semiconductor chiphaving the pads 14 or from the opposite surface to the pads 14.Alternatively, the laser beams may be irradiated from both surfaces(sequentially or simultaneously). It is also possible to form in advancea recess (not shown) at the position of the semiconductor chip 10 atwhich the hole 18 is formed, and to use the recess as a mark for laserbeam irradiation.

A taper 20 may be applied to the hole 18 so that an open width becomesprogressively greater away from the pad 14 as shown in the drawings. Onthe contrary, the taper maybe applied so that the open width becomesprogressively smaller away from the pad 14. Further, the hole 18 mayhave an inner wall surface vertical to the surface of the semiconductorchip 10, separately from the taper.

The insulating material 22 is provided in an area inclusive of the innersurface of the hole 18 as shown in FIG. 1C. The insulating material 22may bury the hole 18, or may be provided on the inner wall surface insuch a fashion as to avoid the center axis of the hole 18. In eithercase, the insulating material 22 may be so provided as to extend to thesurface of the semiconductor chip 10 opposite to the surface having thepad 14, whenever necessary. In the example shown in the drawing, theinsulating material 22 is provided in such a fashion as to cover thesurface of the semiconductor chip 10 inclusive of the inner surface ofthe hole 18. This arrangement makes it possible to increase thesemiconductor chip 10, to improve the strength and to prevent crack.Even when the semiconductor chip 10 expands and is likely to warp due toinfluences of heat, the insulating material 22 absorbs stress andsuppresses the warp. Note that the insulating material 22 may be appliedby means such as a screen-printing system, an ink jet printer system,chemical vapor deposition (CVD), a spray system and application by usinga dispenser.

When the insulating material 22 buries the hole 18 as shown in FIG. 2A,a penetrating hole 24 is formed within a portion that has been the hole18. The penetrating hole 24 is a hole for providing an electricallyconductive material 40. The penetrating hole 24 is formed to a diametersmaller than that of the hole 18. This arrangement can electricallyinsulate the conductive material 40 applied into the penetrating hole 24from the semiconductor chip 10. The form and the formation method of thehole 18 described already may be employed to form the penetrating hole24. In the example shown in the drawing, the taper 26 is applied to thepenetrating hole 24 so that the open width becomes progressively greateraway from the pad 14.

When the insulating material 22 is formed on the inner wall surface ofthe hole 18, the penetrating hole 24 is formed in the area encompassedby the insulating material separately from the arrangement describedabove.

The conductive film 28 electrically connected to the pad 14 (metal layer16) may be formed in advance on the inner surface of the penetratinghole 24 before the conductive material 40 is provided, as shown in FIG.5, whenever necessary. In other words, the conductive film 28 is soformed as to extend from the pad 14 to the inner surface of thepenetrating hole 24. As shown in the drawing, the conductive film 28 maybe formed on the inner wall surface of the penetrating hole 24 in theproximity of the opening on the side of the pad 14. The conductive film28 may also be formed on the pad 14 in such a fashion as to encompassthe entire outer periphery of the penetrating hole 24, or to keepcontact with a part of the outer periphery. The conductive film 28 canbe formed by means such as sputtering or vacuum deposition. According tothis means, the conductive material 40 provided within the penetratinghole 24 can be connected electrically reliably to the pad 14.

Next, as shown in FIGS. 2B to 3, the conductive material 40 is made toflow into the penetrating hole 24. The following example uses thesemiconductor chip 10 having the penetrating holes 24 formed by themethod described above.

Alternatively, it is possible to use a semiconductor chip fabricated byanother method and provide the conductive material 40 in the penetratinghole of the semiconductor chip. In other words, the method of formingthe penetrating hole is not limited in this embodiment. For example, itis possible to employ a method that forms a thin small hole penetratingthrough the semiconductor chip 10 and then expands the small hole by wetetching to form the penetrating hole. In such a case, the penetratinghole may be formed in such a fashion that the diameter of itsintermediate part is greater than the diameter of the open-end portion.

Next, the conductive material 40 is provided at the open-end portion ofthe penetrating hole 24 on the side of the surface of the semiconductorchip 10 (first surface 30) as shown in FIG. 2B. In other words, theconductive material 40 may be provided on a surface of the semiconductorchip 10 having the pad 14. When the penetrating hole 24 is formed in thepad 14, the conductive material 40 is provided on each pad 14.Alternatively, the conductive material 40 may be provided on a surfaceof the semiconductor chip 10 opposite to the surface having the pad 14.

The conductive material 40 may be formed of a single or plurality ofmetal elements, and the material is not limited so long as it haselectric conductivity. The conductive material maybe a conductive resin,for example. The conductive material 40 includes not only those whichremain solid at a normal temperature but also those which have fluidityat a normal temperature.

In the case of the solid, the shape of the conductive material 40 is notlimited, and the shape may be a sphere, a hemi-sphere, a rectangle(including a cube) and other polyhedrons. The solid conductive material40 may be shaped into a continuous shape such as a wire. In such a case,the conductive material need not be provided for each of a plurality ofpenetrating holes 24.

A wire bonding technology used in fabrication methods of semiconductordevices may be applied to obtain the wire-shaped conductive material. Inother words, a capillary (not shown) through which the wire-shapedconductive wire is passed is arranged on the semiconductor chip 10(while it is laid down horizontally, for example), and the conductivewire is continuously fed out from the distal end of the capillary. Insuch a case, the conductive wire at the distal end of the capillary isfused into a ball shape by using laser, and is arranged on thepenetrating hole 24 by controlling the position of the capillary. Atthis time, the ball-like conductive material may be sucked into thepenetrating hole 24 by controlling a pressure difference as will bedescribed later while it is placed on the penetrating hole 24 or whileit is kept above the penetrating hole 24 in the spaced-apart relation.Since this method need not use the ball-like conductive material havinga small diameter, a semiconductor device can be fabricated at a low costof production through a simple fabrication process.

When the conductive material 40 has fluidity, the conductive material 40preferably has high viscosity to such an extent that when it is providedabove the penetrating hole 24, its fluidization into the penetratinghole 24 can be prevented.

In the example shown in FIG. 2B, the conductive material 40 is a solidmetal sphere. The metal sphere has a volume capable of establishingelectric connection with at least the surface and back of thesemiconductor chip 10. The metal sphere has a volume capable of fillingat least the penetrating hole 24, for example. The metal sphere includesnot only the sphere but also those whose surface is formed by curvesurfaces such as an ellipse. The diameter of the metal sphere ispreferably greater than the open width of the penetrating hole 24 on theside of the first surface 30. Any metal sphere is put on the respectivepenetrating hole 24. More specifically, a part of the metal sphere isfitted into the opening of the penetrating hole 24 so as to position themetal sphere to the penetrating hole 24. Since the solid metal sphere ismerely put in this case, the stress resulting from pressurization doesnot act on the semiconductor chip 10, and the semiconductor chip 10 isnot damaged. The metal sphere may close the opening of the penetratinghole 24. When this method is employed, a pressure difference can beeasily created between the side of the first surface 30 and the side ofthe second surface 32 including the inner surface of the penetratinghole 24 as will be described later. The metal sphere may be made of Au(80%)-Sn (20%), Sn (90%)-Ag (10%), or Bi (97.5%)-Ag (2.5%).

The melting point of the conductive material 40 is not limited, and maybe from about 250 to about 300° C., for example. However, the meltingpoint of the conductive material 40 is preferably higher than theheating temperature of the semiconductor chip 10 in subsequent processsteps. For example, the melting point of the conductive material 40 ispreferably higher than the temperature for re-flowing external terminals(see FIG. 10) provided to the semiconductor device. For, the conductivematerial 40 is prevented from re-melting in subsequent process steps. Inconsequence, the outflow of the conductive material 40 from thepenetrating hole 24 can be prevented in the fabrication process.

The conductive material 40 is melted as shown in FIG. 2C. In the exampleshown in the drawing, a laser beam 34 is irradiated to melt theconductive material 40. In other words, the conductive material 40 islocally heated by using the laser heating method. Since local heatingcan be made in this way, the semiconductor chip 10 is prevented frombeing heated to a high temperature. Therefore, the semiconductor chip 10is prevented from being damaged by heating.

The laser beam 34 maybe irradiated from the first surface 30 on the sidein which the conductive material 40 is provided or from the secondsurface 32 opposite to the first surface 30. When the laser beam 34 isirradiated from the second surface 32, the laser beam 34 is irradiatedthrough the penetrating hole 24. Alternatively, the laser beams 34 maybe irradiated from both sides of the first and second surfaces 30 and 32(either simultaneously or sequentially). This method can uniformly meltthe conductive material 40 as a whole. Being melted, the conductivematerial 40 is allowed to flow into the penetrating hole 24.

After the heating temperature of the conductive material 40 is set,laser power is controlled so that the laser beam 34 reaches the settemperature. This method can heat the conductive material 40 at thecorrect temperature, and can control the flow of the conductive material40 with a high level of accuracy.

When the laser beam 34 is irradiated to a plurality of conductivematerials 40, it is further possible to split the laser beam 34 into aplurality of beams by using a phase grating and to collectivelyirradiate these laser beams 34 to the conductive materials 40 providedin a plurality of penetrating holes 24. This method has highproductivity because it can collectively process the conductive material40 provided at a plurality of positions.

To make the molten conductive material 40 flow into the penetrating hole24, the pressure difference is controlled between the side of the firstsurface 30 and the side of the second surface 32 opposite to the firstsurface 30. More specifically, the atmospheric pressure on the side ofthe second surface 32 is set to a pressure relatively lower than theatmospheric pressure on the side of the first surface 30. In this way,the conductive material 40 is allowed to flow into the penetrating hole24 toward the second surface 32.

For example, the atmospheric pressure on the side of the second surface32 may be reduced from the normal atmospheric pressure. In other words,the molten conductive material 40 may be sucked from the side of thesecond surface 32 through the penetrating hole 24. If the atmosphericpressure on the side of the second surface 32 is lowered, the conductivematerial 40 can be sucked simultaneously from a plurality of penetratingholes 24. Therefore, the molten conductive material 40 at a plurality ofpositions can be easily made to flow into the penetrating holes 24.

Alternatively, the atmospheric pressure on the side of the first surface30 may be pressurized to be higher than the normal atmospheric pressure.Since the molten conductive material 40 at a plurality of positions issimultaneously pressurized from the side of the first surface 30, theconductive material 40 can be easily made to flow into the penetratingholes 24. Note that the atmospheric pressure on the side of the firstsurface 30 may be increased and at the same time, the atmosphericpressure on the side of the second surface 32 may be decreased. In otherwords, atmospheric pressure on both sides may be simultaneouslycontrolled.

The step of controlling atmospheric pressure difference between the sideof the first surface 30 and the second surface 32 may be carried outbefore the conductive material 40 is melted. In other words, apredetermined atmospheric pressure difference has been previouslycreated between the first and second surfaces 30 and 32 before theconductive material 40 is melted. This enables to control the flow ofthe conductive material 40 only by setting the power and irradiationtime of the laser beam 34.

As the conductive material 40 is made to flow by the control of theatmospheric pressure difference between the first and second surfaces 30and 32, the conductive material 40 can be smoothly made to flow within ashort time even if the wettability on the inner surface of thepenetrating hole 24 to the conductive material 40 (solder, for example)is small. Therefore, the material of the inner surface of thepenetrating hole 24 can be selected without considering the wettabilityto solder or the like.

Alternatively, as shown in FIG. 6, a solid conductive material 40 may beplaced over the penetrating hole 24 by utilizing the atmosphericpressure difference between the first and second surfaces 30 and 32before the conductive material 40 is melted. When the atmosphericpressure difference is created between the first and second surfaces 30and 32 as shown in the drawing, a gas stream develops toward the innersurface of the penetrating hole 24 on the side of the first surface 30.In consequence, this gas stream can automatically place the conductivematerial 40 on the penetrating hole 24 only by providing the conductivematerial 40 near the penetrating hole 24. It becomes thus possiblethrough a simple step to place the conductive material 40 on thepenetrating hole 24 without a positioning error.

The conductive material 40 may flow until it protrudes from thepenetrating hole 24 to thereby form a bump 46, as shown in FIG. 3. Thebump 46 protrudes also from the second surface 32. The bump 46 may beformed on a surface opposite to the pad 14. The bump 46 can be formed bycontrolling the parameters such as the quantity and fluidity of theconductive material 40, the atmospheric pressure difference between thefirst and second surfaces 30 and 32, or power and the irradiation timeof the laser beam 32. More specifically, these parameters are controlledso that a surface tension can be created in a bottom surface of themolten conductive material 40 outside the penetrating hole 24.

Another bump 42 protruding from the first surface 30 may be formedoutside the penetrating hole 24 in place of, or simultaneously with, theformation of the bump 46. The bump 42 is formed over the penetratinghole 24, that is, over the pad 14 (metal layer 16). When the bumps areformed on both sides of the semiconductor chip 10, the bump 42 iselectrically connected to the bump 46 through the intermediate part 44of the conductive material 40 put into the penetrating hole 24. The bump42 is preferably shaped so that it can be electrically connected to thepad 14. More specifically, the bump 42 has a diameter greater than thediameter of the hole 18 in which the insulating material 22 is provided,as viewed from a direction perpendicular to the first surface 30. Inconsequence, the conductive material 40 can be provided in thepenetrating hole 24 and electrically connected to the pad 14. Therefore,a step of applying a conductive paste or the like onto the pad 14 forelectrically connecting the conductive material 40 to the pad 14 can beomitted.

Alternatively, the conductive material 40 may be made to flow into thepenetrating hole 24 without forming the bumps 42 and 46. In this case,if the conductive material 40 is provided in the penetrating hole 24without any gap, the mechanical strength of the semiconductor chip 10can be improved. Note that the conductive material 40 is not necessarilybe provided in the penetrating hole 24 without any gap, but may flowinto the penetrating hole 24 to such an extent that the conductionbetween both surfaces of the semiconductor chip 10 can be established.

As shown in FIG. 7, a bump 246 may be formed as to satisfy the relation:A<B between the diameter A of the bump 246 formed of the conductivematerial 240 and protruding from the second surface 32 and the diameterB of the hole 18 in which an insulating material 222 is provided on aninner surface. This configuration is effective when the insulatingmaterial 222 is provided only on the inner surface of the hole 18, asshown in the drawings. In other words, this makes it possible to preventthe electrical conduction between the bump 246 protruding from the hole18 and the semiconductor chip 10 when the insulating material 222 is notprovided on the side opposite to the pad 14 of the semiconductor chip10. Moreover, since the insulating material 222 is not required to beextended to the surface of the semiconductor chip 10, the amount of theinsulating material 222 can be reduced.

It is further possible to stack a plurality of semiconductor devices 1and to electrically connect the upper and lower semiconductor chips 10through the conductive material 40 as shown in FIG. 4. In other words, asemiconductor device having a three-dimensional configuration isfabricated. As shown in this drawing, each semiconductor chip 10 may bestacked in such a fashion that the surface having the pads 14 faces inthe same direction. Alternatively, the semiconductor chip 10 may bestacked in such a fashion that the surface having the pads 14 opposesone another, or the surface opposite to the surface having the pads 14opposes one another.

When each semiconductor device 1 has the bumps 46, the upper and lowersemiconductor chips 10 may be electrically connected with one another byusing the bumps 46. This configuration eliminates the necessity forforming the external terminals and can therefore simplify thefabrication steps.

Separately from the example shown in the drawing, the external terminals(of a brazing material such as the solder) may be provided to the bump46 of the semiconductor chip 10 (the portion of the conductive material40 exposed to the opening of the penetrating hole 24 when the bump 46 isnot formed). Particularly when the bump 46 is formed on thesemiconductor chip 10, the external terminal can be connectedelectrically reliably to the conductive material 40. When the externalterminal is provided, each semiconductor chip 10 can be connectedelectrically reliably. Note that the external terminal may be providedto only the semiconductor chip 10 of the lowermost stage that isdirectly mounted to the circuit board.

Alternatively, it is possible to employ the configuration in which thesemiconductor chips 10 are stacked in such a fashion that the upper andlower penetrating holes 24 overlap plane-wise with one another, toarrange the conductive material 40 over the penetrating hole 24 formedin the semiconductor chip 10 of the uppermost stage, and to melt theconductive material 40 so as to let it flow into a plurality ofpenetrating holes 24 of the upper and lower stages. This configurationmakes it possible to collectively provide the conductive material 40 inthe penetrating holes 24 of a plurality of semiconductor chips 10 and toelectrically connect the upper and lower semiconductor chips 10.

According to the fabrication method of the semiconductor device in thisembodiment, the molten conductive material 40 is made to flow into thepenetrating holes 24 toward the second surface 32 when the atmosphericpressure on the side of the second surface 32 is lower than that of theside of the first surface 30. Since this method causes the moltenconductive material 40 to flow while controlling the atmosphericpressure difference, the conductive material 40 can be provided in thepenetrating holes 24 in a short time. Since this method puts theconductive material 40 over the penetrating holes 24 and then melts it,the process step is simple.

Next, a semiconductor device according to this embodiment will bedescribed. As shown in FIG. 3, the semiconductor device 1 includes asemiconductor chip 10 having penetrating holes 24 and a conductivematerial 40 provided in an area inclusive of the inner surface of eachpenetrating hole 24. Part of the conductive material 40 protrudes from asurface (second surface) opposite to the surface (first surface 30) ofthe semiconductor chip 10 on which pads 14 are formed.

As shown in FIG. 4, this semiconductor device 3 includes a plurality ofsemiconductor devices 1 that are stacked one upon another. Eachsemiconductor chip 10 is electrically connected with others through theconductive material 40. Note that the rest of the components of thesesemiconductor devices 1 and 3 are described in the above fabricationmethod.

When part of the conductive material 40 provided in the penetrating hole24 protrudes from the surface of the semiconductor chip 10 in thesesemiconductor devices, the protruding portion (bump 46) is used as theexternal terminal and by so doing, the number of components of thesemiconductor devices can be decreased. Therefore, the semiconductordevices can be provided at a reduced cost of production.

Second Embodiment

FIGS. 8A to 8C show a fabrication method of a semiconductor deviceaccording to the second embodiment of the invention. The technicalcontent of the first embodiment can be applied as much as possible tothis embodiment. In this embodiment, a conductive material 140 is madeto flow into penetrating holes 24 of a semiconductor wafer 110.

As shown in FIG. 8A, the semiconductor wafer 110 (semiconductor chip) isfirst prepared. The semiconductor wafer 110 has a plurality ofpenetrating holes 24. The form and the formation method of thepenetrating holes 24 of the foregoing examples can be applied.

The conductor material 140 is placed on the first surface 30 of thesemiconductor wafer 110 above the penetrating holes 24 as shown in FIG.8B. The conductor material 140 is paste-like such as a solder paste. Theconductor material 140 may be applied by means such as a screen-printingsystem and application by using a dispenser. Particularly when thedispenser is used, the conductive material 140 can be applied withoutimparting damage to the semiconductor wafer 110. The conductive material140 may be applied also by using an ink jet system. According to thissystem, the conductive material 140 can be applied at a high speed andeconomically without waste.

The conductive material 140 may be provided at a plurality of positionswhere the penetrating holes 24 are formed as shown in the drawing, ormay be integrally provided in an area inclusive of a plurality ofpenetrating holes 24. In the latter case, the conductive material 140may be provided in such a fashion as to cover the first surface 30 ofthe semiconductor wafer 110. According to this method, the conductivematerial 140 can be easily provided without taking the correct positionsinto consideration.

After provided, the conductive material 140 is melted. In the exampleshown in the drawing, the conductive material 140 is heated by using aheater 50. The heater 50 may use infrared rays, for example, or may havea known configuration such as the one in which hot wind, hightemperature atmosphere (e.g. N₂ re-flow oven) or heated jig is broughtinto contact with the conductive material 140. When the heater 50 heatsthe semiconductor wafer 110, the conductive material 140 provided over aplurality of penetrating holes 24 can be simultaneously melted.Therefore, the heating step is simple. The heater 50 may be provided onthe side of the first surface 30 of the semiconductor wafer 110 or onthe side of the second surface 32 or on both sides.

To make the molten conductive material 140 flow into the penetratingholes 24, the atmospheric pressure difference between the first andsecond surfaces 30 and 32 is controlled. The detail of this control isdescribed in the first embodiment.

The conductive material 140 can be provided in this way in thepenetrating holes 24 as shown in FIG. 8C. When the conductive material140 is provided integrally in the area inclusive of a plurality ofpenetrating holes 24 (such as the entire part of the first surface 30),washing is thereafter carried out. In other words, the conductivematerial 140 applied to portions other than the penetrating hole 24 areais removed from among the conductive material 140 remaining on the firstsurface 30.

After the conductive material 140 is thus provided in the penetratingholes 24, the semiconductor wafer 110 is diced and split into aplurality of semiconductor chips. Alternatively, after a plurality ofsemiconductor wafers 110 is stacked in a vertical direction, a pluralityof the upper and lower semiconductor wafers 110 may be dicedsimultaneously.

The fabrication method of the semiconductor device according to thisembodiment can be conducted by selecting any of the technical contentsdescribed in the first embodiment. For example, a solid conductivematerial (such as metal spheres) may be provided on the semiconductorwafer 110, or a paste-like conductive material 140 may be melted by theirradiation of laser beams. The technical content of this embodiment mayalso be applied to the semiconductor chip described in the firstembodiment.

The second embodiment of the present invention can accomplish theeffects described in the first embodiment.

Third Embodiment

FIGS. 9A to 9C show a fabrication method of a semiconductor deviceaccording to the third embodiment of the present invention. Thetechnical content of the first and second embodiments can be applied asmuch as possible to this embodiment. In this embodiment, a conductivematerial 40 is provided in penetrating holes 66 of a board 60.

A board 60 is first prepared as shown in FIG. 9A. The board 60 may bemade of an organic material (resin type) or an inorganic material(ceramic type, metal type) or their composite system. The board 60 mayuse a glass epoxy board or a polyimide board, for example. The overallshape of the board 60 is not limited, but is in most cases similar tothe planar shape of the semiconductor chip 10. The thickness of theboard 60 is decided in accordance with its material and is notparticularly limited. The board 60 may have a single layer or multiplelayers.

An interconnecting pattern 62 is formed on the board 60. Theinterconnecting pattern 62 includes in most cases a plurality of layersof copper, nickel or gold. The interconnecting pattern 62 may be formedon both surfaces of the board 60 as shown in the drawing or on only oneof the surfaces.

The interconnecting pattern 62 includes in most cases lands 64 (orpads). The land 64 has a width greater than that of a line connectedthereto. The shape of the land 64 may be circular. In this case, theland 64 has a diameter greater than the width of the line.Alternatively, the interconnecting pattern of only lines may be formedon the board 60 without forming the lands 64.

The board 60 may be an interposer for a semiconductor package or a boardfor MCM (Multi-Chip Module) or a board for a motherboard, and itsapplication is not limited. The board 60 may further be a build-upmulti-layered printed wiring board.

Penetrating holes 66 are formed in the board 60. When the lands 64 areformed, the penetrating holes 66 are formed to penetrate the lands 64.According to this arrangement, the conductive material 40 can beelectrically connected to the interconnecting pattern 62 as it isallowed to flow into the penetrating holes 66. In the example shown inthe drawing, the lands 64 are formed on both surfaces of the board 60 insuch a fashion as to superpose plane-wise with one another, and thepenetrating hole 66 is formed in such a fashion as to open the center ofthe land 64 on each surface.

As described, a conductive film extending from the land 64 into thepenetrating hole 66 may be formed before the conductive material 40 isprovided. The conductive film can connect electrically reliably the land64 and the conductive material 40.

The conductive material 40 is provided on the first surface 70 of theboard 60 above the penetrating hole 66 as shown in FIG. 9B. Thecomposition of the conductive material 40 is described in the firstembodiment. In the example shown in the drawing, a solid metal sphere isplaced over the penetrating hole 66, and the laser beam 34 is irradiatethe metal sphere to melt it. The atmospheric pressure on the side of thesecond surface 72 opposite to the first surface 70 is reduced to berelatively lower than the atmospheric pressure on the side of the firstsurface 70 so that the conductive material 40 can be made to flow towardthe second surface 72 through the penetrating hole 66.

Alternatively, the conductive material may use a paste-like material. Aheater may be used to melt the conductive material 40. In such a case,the board 60 may be heated. These technical contents are the same asthose described in the second embodiment.

The conductive material 40 flows into the penetrating hole 66, as shownin FIG. 9C. Since the penetrating hole 66 of the board 60 is filled, themechanical strength of the board 60 can be improved. The conductivematerial 40 may be provided in the penetrating hole 66 as shown in thedrawings, or may be provided to form a bump outside the penetrating hole66.

The third embodiment of the present invention can accomplish the sameeffect as described in the first and second embodiments. Theconfiguration of the wiring board 5 in this embodiment is as describedabove.

FIG. 10 shows a circuit board 80 over which the semiconductor device 3described in the first embodiment is mounted. The circuit board 80 maybe a mother board. An organic board such as a glass epoxy board or apolyimide film, or a glass board such as a liquid crystal display boardis generally used for the circuit board 80. An interconnecting pattern82 made of copper, for example, is formed on the circuit board 80 toobtain a desired circuit, and is electrically connected to thesemiconductor device 3. The semiconductor device 3 may be electricallyconnected to the circuit board 80 by mechanically connecting externalterminals 90 to the interconnecting pattern 82, for example.

As examples of electronic instruments including the semiconductor device3 to which the present invention is applied, there are a notebookcomputer 100 shown in FIG. 11 and a cellular phone 200 shown in FIG. 12.

What is claimed is:
 1. A method of fabricating a semiconductor devicecomprising the steps of: providing a conductive material to an open endof a penetrating hole penetrating through at least a semiconductorelement, on the side of a first surface of the semiconductor element;and melting the conductive material to make the conductive material flowinto the penetrating hole, wherein the conductive material is made toflow into the penetrating hole in a state that an atmospheric pressureon the side of a second surface of the semiconductor element opposite tothe first surface is lower than an atmospheric pressure on the side ofthe first surface.
 2. The method of fabricating a semiconductor deviceas defined in claim 1, wherein the semiconductor element has a padformed on the first surface; and wherein the penetrating hole penetratesthrough the pad.
 3. The method of fabricating a semiconductor device asdefined in claim 2, wherein a conductive film extending from the padinto an inner surface of the penetrating hole is formed before theconductive material is provided.
 4. The method of fabricating asemiconductor device as defined in claim 1, wherein the conductivematerial is a solid, and the solid conductive material is placed overthe open end of the penetrating hole on the side of the first surface.5. The method of fabricating a semiconductor device as defined in claim1, wherein the conductive material is paste-like, and the paste-likeconductive material is applied to the open end of the penetrating holeon the side of the first surface.
 6. The method of fabricating asemiconductor device as defined in claim 5, wherein the paste-likeconductive material is applied to the first surface of the semiconductorelement.
 7. The method of fabricating a semiconductor device as definedin claim 1, wherein a laser beam is projected onto the conductivematerial to melt the conductive material.
 8. The method of fabricating asemiconductor device as defined in claim 1, wherein the semiconductorelement is heated to melt the conductive material.
 9. The method offabricating a semiconductor device as defined in claim 1, wherein theconductive material is made to flow in a state that an atmosphericpressure on the side of the first surface of the semiconductor elementis higher than normal atmospheric pressure.
 10. The method offabricating a semiconductor device as defined in claim 1, wherein theconductive material is made to flow in a state that an atmosphericpressure on the side of the second surface of the semiconductor elementis lower than normal atmospheric pressure.
 11. The method of fabricatinga semiconductor device as defined in claim 1, wherein the conductivematerial is made to flow through the penetrating hole and protrude fromthe second surface into a bump.
 12. The method of fabricating asemiconductor device as defined in claim 11, wherein the penetratinghole is formed as a hole in the semiconductor element, an inner wall ofthe hole being covered by an insulating material; and wherein thediameter of the bump is smaller than the diameter of the hole.
 13. Themethod of fabricating a semiconductor device as defined in claim 1,wherein the semiconductor element is a semiconductor wafer.
 14. A methodof fabricating a stacked type semiconductor device comprising the stepsof: forming a plurality of semiconductor devices each of which is formedby: providing a conductive material to an open end of a penetrating holepenetrating through at least a semiconductor element, on the side of afirst surface of the semiconductor element; melting the conductivematerial to make the conductive material flow into the penetrating hole;and causing the conductive material to flow into the penetrating hole ina state that an atmospheric pressure on the side of a second surface ofthe semiconductor element opposite to the first surface is lower than anatmospheric pressure on the side of the first surface; stacking theplurality of the semiconductor devices; and electrically connecting thesemiconductor elements of the stacked semiconductor devices through theconductive material.
 15. A semiconductor device fabricated by the methodas defined in claim
 1. 16. A stacked type semiconductor devicefabricated by the method as defined in claim 14.